An edged tool such as a knife, scalpel, razor blade, and the like, is typically formed from metal, ceramic, glass or other vitreous material and possesses at least one generally V-shaped cutting edge. In the case of a razor blade, the cutting edge usually possesses a radius of less than about 1,000 angstroms and an included angle of less than 30°. Shaving action can be severe and may result in damage to the blade edge. It has therefore been a common practice to provide the cutting edge of a razor blade with one or more coatings in order to increase the hardness and/or corrosion resistance of the cutting edge, to facilitate shaving with an increase in comfort to the user and/or to achieve some other advantageous result.
Among the coating materials that have been used and/or proposed for coating cutting edges, in particular, those of a razor blade, are thermoplastic materials such as polyethylene, halogenated polymers and telomers (low molecular weight polymers), and the like. See, e.g. in this regard, U.S. Pat. Nos. 3,224,900, 3,518,110, 3,658,742, 5,263,256 and 5,985,459 which disclose various polymeric coatings for cutting edge(s) of razor blades and methods of applying the coatings to the edge(s). The contents of these patents are incorporated by reference herein and are annexed hereto as an integral part of the disclosure of this application.
One method of applying the thermoplastic coating material to the cutting edge(s) of a razor blade involves spraying a suspension of dispersion of the coating material upon the edge(s) and thereafter heating the blade in a non-oxidizing environment to cause the polymeric material to melt and spread evenly over the blade edge surfaces. With the cooling of the blade, the coating material solidifies and remains adhered to the cutting edge(s). Heating the blade to produce this melting has, in general, been accomplished by infrared heating, inductive heating or resistance heating of the blade, e.g., at temperatures of from about 200° C. to about 400° C. Examples of such coating processes are disclosed in e.g., aforesaid U.S. Pat. Nos. 3,224,900, 3,518,110, 3,658,742, 5,263,256 and 5,985,459.
Resistance and inductive heating involve relatively high energy consumption and take a comparatively long time to heat the blades to the required temperatures for melting of the polymer. Since these heating operations result in heating the entire body of the blade including the blade carrier, they consume more heat than would be required to melt just the polymer which is confined to the edge(s) of the blades. Although infrared heating is somewhat faster than resistance or inductive heating (which can take about 60-90 minutes to heat a 12 inch stack of blades), it still requires a fairly long period of time to heat the polymer particles to the melt temperature and a relatively long time to cool the blade body sufficiently for the fused polymer particles to solidify.
In addition to the high energy consumption and processing periods associated with the above-discussed coating methods, such heating may negatively affect the temper of the blades.
Microwave energy has heretofore been used to apply polymeric materials to the surfaces of various substrates. See, e.g., in this regard, U.S. Pat. Nos. 5,422,146, 5,804,801 and 5,879,756. The contents of these patents are incorporated by reference herein and are annexed hereto as an integral part of the disclosure of this invention. However, it is believed that microwave energy has not previously been disclosed for melting fusible coating materials applied to the cutting edges of razor blades or other cutting tools.
It is an object of the invention to provide an improvement in the above-discussed prior art coating methods by applying a coating containing a fusible polymeric material to a cutting edge of an edged tool and fusing (melting) the polymer employing microwave energy as the heat source.